An automatic transmission for a vehicle is provided with a line pressure control device which comprises an oil pump and a pressure regulator valve. The line pressure control device controls the line pressure supplied to a speed ratio varying mechanism which varies a speed ratio and a clutch mechanism which switches a direction of transmission of the drive force. Tokkai Hei 8-28646 published by the Japanese Patent Office in 1996 discloses a line pressure control device which raises a line pressure in response to torque input into the transmission.